Tuesday, February 19, 2013

P.P.S (I usually put post-scripts at the end of the post, but this one so fundamentally changes the nature of the AHA's press release, you need to see it first.)

The lead researcher on the study below was one Christopher E. Ramsden. Turns out he and the AHA have a history, the AHA posted this letter from him in 2009 concerning the Sydney Diet-Heart Study:

"Regrettably, the recent AHA Advisory [1] relied heavily upon a one-line meta-analysis
cited in a non peer-reviewed book chapter [2] to support its position that high intakes of omega-
6 fatty acids reduce CHD. Unfortunately, the credibility of this advisory is undermined by four
additional critical errors.

1) The AHA Advisory mistakenly cited the Sydney Diet-Heart Study [3] when referring to
Gordon’s meta-analysis [2] and its ascribed conclusion that “PUFA lowered the risk of CHD
events by 24%” [1]. The Sydney study did not report CHD events and was not included in
Gordon’s analysis of CHD events. Importantly, the study did report that 39 of 221 (18%) high
omega-6 [Linoleic Acid] dieters died within 5 years versus only 28 of 237 (12%) of controls, and that 63 of
67 (94%) of these deaths were due to CV disease [3]. This 49% increased death rate in the
high-LA group warrants attention and discussion in any balanced review of published evidence....

This casts a new light on the AHA's dismissal of this new research. Circle the wagons, indeed.

"A recent study published in the British Medical Journal analyzed data from the late 60’s and early 70’s and concluded that substituting polyunsaturated fats (PUFAs), rich in Omega-6 linoleic acid, for saturated fats did not result in cardiovascular benefits among a group of men who had experienced a heart attack or other cardiac event...."

"...The results show that the omega-6 linoleic acid group had a higher risk of death from all causes, as well as from cardiovascular disease and coronary heart disease, compared with the control group...."

"...However, the researchers admitted their analysis was limited by the fact that they did not have access to the original study protocol, so they could not fully appraise its accuracy.

“The British Medical Journal study is interesting, but not conclusive. It is offset by a large body of scientific evidence that continues to show cardiovascular benefits associated with eating mono- and poly-unsaturated fat, rich in Omega-6 linoleic acids, in place of saturated fats...”

Again, from the study:

"Without access to the original study protocol, we cannot fully appraise the accuracy of outcome ascertainment and other quality aspects of the SDHS. Another potential limitation was incomplete data recovery, owing to our inability to identify some of the study variables recorded on punch cards. However, we were able to identify, confirm, and verify each of the key variables for the dietary, laboratory, and coded mortality outcomes that were required to interpret the main study findings (web appendix, part 1)."

The professor doesn't address the part after the "however", nor does she address this:

"“The British Medical Journal study is interesting, but not conclusive. It is offset by a large body of scientific evidence that continues to show cardiovascular benefits associated with eating mono- and poly-unsaturated fat, rich in Omega-6 linoleic acids, in place of saturated fats,”"

So there either is or is not evidence. But the BMJ study at least presents some, the AHA merely asserts its authority and dismisses the study, ignoring the bulk of it, and finding fault with a technical aspect.

Of course the AHA led with their strongest salvo:

"The association bases its recommendations on a robust body of scientific studies that demonstrate a strong association between eating a diet high in saturated fat and the development of atherosclerosis, which clogs arteries and causes heart disease."